As the critical dimension of metal oxide semiconductor field effect transistor (MOSFET) devices continues to shrink, the short channel effect becomes more problematic. Fin field effect transistor (FinFET) devices have good control capability of gates to effectively suppress the short channel effect. FinFET devices can also reduce random dopant fluctuation to improve the stability of the devices. Thus, FinFET devices are widely used in the design of small-sized semiconductor elements.
In the manufacturing process of a FinFET device, under normal circumstances, three conditions may exist for performing a well implantation (including an N-well and a P-well): a well implant may be formed (1) before forming the fins, (2) after the planarization of the shallow trench isolation (STI) structure, or (3) after forming the fins.
In the case that the N-well and P-well are formed before the formation of the fins, because a flowable chemical vapor deposition (FCVD) process is used to fill the gap spaces between the fins with an oxide material after the fins are formed, the dopant ions, especially dopant ions implanted into the P-well may diffuse into the oxide material, resulting in the loss of the implanted dopant ions.
In the case that the N-well and P-well are formed after the planarization of the STI structure, because of the hardmask over the STI structure, the implantation of dopant ions requires a high ion energy.
In the case that the N-well and P-well are formed after the formation of the fins, the implanted dopant ions may cause damage to the fins. Especially, the N-well implant requires a relatively high ion energy that may cause severe damage to the fins.
Therefore, there is a need for improved methods for manufacturing a fin-type semiconductor device to overcome the above drawbacks.